Nur77, an orphan receptor of the steroid/thyroid hormone nuclear receptor superfamily, is widely expressed in the central nervous system (CNS) including brain regions where the opoid peptides enkephalin and dynorphin are abundant, such as the striatum, cortex, and central amygdala. Expression of Nur77 in motor areas of the cortex and basal ganglia suggest a role for this transcription factor in regulation of motor functions and reward mechanisms. To better understand the effects of Nur77 in the CNS we investigated the degree of co-existence of Nur77 with preproenkephalin and prodynorphin mRNA in the adult rat brain. Nur77 and preproenkephalin co-localization was observed in striatal areas, olfactory tubercle and central amygdala. Prodynorphin and Nur77 co-expression was also observed in the striatum and central amygdala, as well as in the supraoptic nucleus. Nur77 expression was absent in prodynorphin positive neurons in the cortex. These results clearly demonstrate that Nur77 is expressed in various opiate-peptide positive neuronal populations and suggest that Nur77 may have a gene regulatory role in specific peptide-positive neurons throughout the CNS.